The importance of chiral, nonracemic structural units in a number of biologically active compounds has led to intensive efforts to develop efficient syntheses for these compounds. Chiral auxiliary mediated asymmetric synthesis has played an important role in the development of a range of chemical transformations that can be carried out with the high degree of absolute stereocontrol necessary for effective assemblage of biologically important compounds.
Enantiopure (-)-8-phenylmenthol (Formula VII) ##STR6## is a highly efficient chiral auxiliary which has been demonstrated to have powerful stereochemical directing influences in several types of synthetically useful reactions. See generally Oppolzer et al., Helv. Chim. Acta 63:2015 (1980); see also Whitesell, Acc. Chem. Res. 18:280 (1985). This chiral auxiliary is commercially available but expensive. Alternatively, the compound can be prepared from (+)-pulegone in five synthetic steps. Both the cost of the compound and its lengthy synthesis restrict its industrial use. Furthermore, the enantiomer of the compound of Formula (VII), (+)-8-phenylmenthol, is very expensive and requires a complicated synthesis with many steps.
Accordingly, there is a clear need for inexpensive, readily available chiral compounds. There is a similar need for the enantiomers of such compounds. Finally, there is a need for a relatively simple process to make and separate such enantiomers.